Structural health monitoring of adhesive joints under pure mode I loading using the electrical impedance measurement

In the recent years, the piezoelectric wafer active sensors (PWASs) are increasing as a measurement tool in structural health monitoring techniques. In impedance-based structural health monitoring (ISHM) method, the electrical impedance of a PWAS bonded to the structure is measured and served as a defect detection index of the structure. The principle of this method is based on the electromechanical coupling effect of PWAS materials. As any change in the structure will lead to a change in mechanical impedance of structure, the electrical impedance of PWAS could sense this change by the electromechanical coupling effect of PWAS. Since the physical and mechanical properties of PWAS materials are temperature-dependent, so the electrical impedance of PWAS will change with varying temperature. Consequently, the changes in environmental or service temperatures could be detected in ISHM method as a defect. In this article, in order to consider the temperature dependency of PWAS material properties, a temperature-dependent model is developed for a PWAS bonded to an Euler Bernoulli cantilever beam. An aluminum (alloy 2024) beam was examined experimentally by ISHM method in order to validate the proposed model. The comparison of theoretical and experimental results demonstrates a good improvement in ISHM modeling where temperature variation is present.

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Electromechanical Impedance Modeling for Structural Health Monitoring

Volume 1: Development and Characterization of Multifunctional Materials; Modeling, Simulation and Control of Adaptive Systems; Structural Health Monitoring ◽

10.1115/smasis2012-8094 ◽

2012 ◽

Author(s):

Liuxian Zhao ◽

Lingyu Yu ◽

Mattieu Gresil ◽

Michael Sutton ◽

Siming Guo

Keyword(s):

Structural Health Monitoring ◽

Health Monitoring ◽

Electrical Impedance ◽

Piezoelectric Materials ◽

Fiber Composite ◽

Mechanical Impedance ◽

Experimental Result ◽

Electromechanical Impedance ◽

Structural Health ◽

Aluminum Beam

Electromechanical impedance (EMI) method is an effective and powerful technique in structural health monitoring (SHM) which couples the mechanical impedance of host structure with the electrical impedance measured at the piezoelectric wafer active sensor (PWAS) transducer terminals. Due to the electromechanical coupling in piezoelectric materials, changes in structural mechanical impedance are reflected in the electrical impedance measured at the PWAS. Therefore, the structural mechanical resonances are reflected in a virtually identical spectrum of peaks and valleys in the real part of the measured EMI. Multi-physics based finite element method (MP-FEM) has been widely used for the analysis of piezoelectric materials and structures. It uses finite elements taking both electrical and mechanical DOF’s into consideration, which allows good differentiation of complicated structural geometries and damaged areas. In this paper, MP-FEM was then used to simulate PWAS EMI for the goal of SHM. EMI of free PWAS was first simulated and compared with experimental result. Then the constrained PWAS was studied. EMI of both metallic and glass fiber composite materials were simulated. The first case is the constrained PWAS on aluminum beam with various dimensions. The second case studies the sensitivity range of the EMI approach for damage detection on aluminum beam using a set of specimens with cracks at different locations. In the third case, structural damping effects were also studied in this paper.. Our results have also shown that the imaginary part of the impedance and admittance can be used for sensor self-diagnosis.

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A Comparative Study of Impedance Measurement Techniques for Structural Health Monitoring Applications

IEEE Transactions on Instrumentation and Measurement ◽

10.1109/tim.2018.2792854 ◽

2018 ◽

Vol 67 (4) ◽

pp. 912-924 ◽

Cited By ~ 18

Author(s):

Danilo Ecidir Budoya ◽

Fabricio Guimaraes Baptista

Keyword(s):

Structural Health Monitoring ◽

Comparative Study ◽

Health Monitoring ◽

Measurement Techniques ◽

Impedance Measurement ◽

Structural Health ◽

Monitoring Applications

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On the inverse determination of displacements, strains, and stresses in a carbon nanofiber/polyurethane nanocomposite from conductivity data obtained via electrical impedance tomography

Journal of Intelligent Material Systems and Structures ◽

10.1177/1045389x17692053 ◽

2017 ◽

Vol 28 (18) ◽

pp. 2617-2629 ◽

Cited By ~ 20

Author(s):

TN Tallman ◽

S Gungor ◽

GM Koo ◽

CE Bakis

Keyword(s):

Structural Health Monitoring ◽

Electrical Impedance Tomography ◽

Health Monitoring ◽

Electrical Impedance ◽

Carbon Nanofiber ◽

Constitutive Relations ◽

Full Potential ◽

Conductivity Data ◽

Impedance Tomography ◽

Structural Health

Carbon nanofiller-modified composites possess extraordinary potential for structural health monitoring because they are piezoresistive and therefore self-sensing. To date, considerable work has been done to understand how strain affects nanocomposite conductivity and to utilize electrical impedance tomography for detecting strain or damage-induced conductivity changes. Merely detecting the occurrence of mechanical effects, however, does not realize the full potential of piezoresistive nanomaterials. Rather, knowing the mechanical state that results in the observed conductivity changes would be much more valuable from a structural health monitoring perspective. Herein, we make use of an analytical piezoresistivity model to inversely determine the displacement field of a strained carbon nanofiber/polyurethane nanocomposite from conductivity changes obtained via electrical impedance tomography. From the displacements, kinematic and constitutive relations are used to calculate strains and stresses, respectively. A commercial finite element simulation is then used to validate the accuracy of these predictions. These results concretely demonstrate that it is possible to inversely determine displacements, strains, and stresses from conductivity data thereby enabling unprecedented insight into the mechanical response of piezoresistive nanofiller-modified materials and structures.

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MWCNT-Epoxy Nanocomposite Sensors for Structural Health Monitoring

10.20944/preprints201807.0419.v1 ◽

2018 ◽

Author(s):

Omid Sam-DaIiri ◽

Lisa-Marie Faller ◽

Mohammadreza Farahani ◽

Ali Roshanghias ◽

Hannes Oberlercher ◽

...

Keyword(s):

Structural Health Monitoring ◽

Health Monitoring ◽

Impedance Measurement ◽

Building Structures ◽

Adhesive Bonds ◽

Multi Wall Carbon Nanotubes ◽

Structural Health ◽

Nanocomposite Sensors ◽

Parallel Resistance ◽

Alternating Voltage

We address Multi-Wall Carbon NanoTubes (MWCNTs) for structural health monitoring in adhesive bonds such as in building structures. MWCNT-loaded composites are employed to sense strain changes under tension load using an AC impedance measurement setup. Different weight percentages of 1, 1.5, 2 and 3 wt.% MWCNT are added to the base epoxy resin using different dispersion times, i.e. 5, 10 and 15 minutes. The equivalent parallel resistance of the specimens is measured by applying an alternating voltage at different frequencies. To determine the mechanical as well as sensory properties, the specimens are subjected to a tensile test with concurrent impedance measurement. Using alternating voltage, a higher sensitivity of the impedance reading can be achieved. Employing these sensors in buildings and combining the readings of a network of such devices can significantly improve the buildings’ safety. Additionally, networks of such sensors can be used to identify necessary maintenance actions and locations.   

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